Hydraulic valve tappet



Aug. 20, v1 957 G. T. RANDOL HYDRAULIC VALVE TAPPET Filed may 2, 195e 2 Sheets-Sheet 1 Inventor Aug. 2o, 1957 Filed May 2, 1956' G. T. RAND'OL 2,803,232

HYDRAULIC VALVE TAPPET 2 Sheets-Sheet 2 9a L f v7 l 33 30a a@ J5@ .fs J7 62 a 5' @E l 85 fOa 2,803,232 HYDRAULIC VALVE TAPPET Glenn T. Randol, Mountain Lake Park, Md. Application May 2, 1956, serial No. 532,181

27 Claims. (ci. 12s- 90) This invention relates generally to hydraulic means for automatically taking up backlash or play in valveactuat` ing tappet mechanism, and more particularly to such mechanism for incorporation in the valve drive train of internal-combustion engines, especially of the overhead valve, cam-actuated type.

My present invention has for its primary object to provide a simple and eicient automatically adjustable hydraulic tappet for internal-combustion engines, and to such ends, generally stated, the invention consists ofthe novel devices and combinations of devices hereinafter described and defined in the claims.

This improved tappet, while capable of more general use, is especially designed for and will be found particularly adapted to engines of the overhead valve type, wherein long push rods are disposed between the engine driven camshaft and the rocker arms, that directly act on the valves.

Valve operating mechanisms of internal-combustion engines generally comprise a valve train or gear of several engaging parts which transmit thrust-motion from an eccentric cam to a poppet valve. As the operating clearances between the engaging parts of the drive train vary to a considerable extent because of temperature variations and 'wear it is difficult to effect stable, silent and eicient operation of the engine. Accordingly, it is desirable to provide means in the train for compensating for suc conditions.

Conventional hydraulic tappets have found wide accepti However,

States PatentY @ffice 2,803,232 Patented Aug. 20, 1957 tion to closed ,position supplemented by high pressure conditions within the high pressure chamber, and by the action of an inertia hammer or weight in its upward throw induced by initial tappet movement to open an engine valve, said weight being opposed by a preloaded snubber spring carried by said valve element to transmit the weight thrust` tosaid element to assist in holding the latter closed, and to accelerate the downward movement of said weight into impact with the valve element to open the same upon theV engine valve becoming closed, notwithstanding the then existent pressure differentials across opposite sides offthe 4valve element and spring tension thereon tending to oppose such valve opening action of the inertia hammer.

.An object related to the object immediately above is-to incorporate in said tappet mechanism, novel and improved valve means controlled by a weight or inertia hammer in such manner that the motion of the tappet assembly operates to thro'w the weight, on the opening cycle of the `engine valve, in a direction to supplement a preloaded spring `and modulated pressure conditions of the fluid trapped in the high pressure chamber induced by the closing of said valve means to rmly seat the latter while the engine-operated cam inaugurates opening the selected engine valve; while upon the tappet assembly reaching substantially engine valve closed condition, the Weight moves downwardly into impact with the valve means to open the same to enable the engine .valve drive mechanism tofeompensate for any backlash condition which may exist, said spring acting to restore the valve means and inertia mechanism to lightly seated relationship with respect to the port controlling huid communication between said chambers, the tappet u nit engaging the base circle of the engine-driven cam during spring restorative action to-.preloaded status whereby uid communication is reestablished viay said port between said chambers in readiness for another engine valve opening cycle.

`-Another object is to operably associate with said low pressure chamber, a movable piston assembly including a preloaded compression spring for normally establishing predetermined low pressure conditions within both chambers while said check-valve is open or lightly seated against'said port.

kA further salient feature of the present invention resides inthe novel counterbalancing substantially of the forces engendered by the check-valve return seating spring aforesaid andthe static weight of the inertia mechanism wherebythe check-valve remains open to enable compensating adjustments of the tappet for substantially the full duration of tappet body engagement with the base circle of the It is, therefore, an important object of the present in- A' vention to provide an improved hydraulic tappet which does not utilize engine lubricant from the oil pan, thus engine-operated cam.

Another important object in tappet construction of the typeV under consideration wherein two cylindrical members` are interittedin closely established clearance there- "between,rif desired, to enable a controlled amount of oil to escape from below and past the inner member, to provide relative movement leakdown between said members to'establish an appropriate operating clearance in the engine vvalve operating linkage during the lift portion of '.-`the"tappet cycle, is the novel provision of controlled leakwithin the tappet, and normally subjected to a predetermined pressure when installed, and does not require replenishment nor can the fluid become contaminated.

A further object related to the object next above is the novel provision for utilizing ordinary engine lubricants in the tappet under consideration, and therefore,` iluids4 down via the check-valve alone, so that leakdown and recovery Vrates are not only consistent irrespective of engine speeds but also more rapid, particularly in respect to the recovery rate. However, the present tappet construction contemplates use of clearance control and will having special characteristics are not required for the eflicient operation of the present tappet mechanism.

Another important object is the provision of novel tappet construction comprising high and lowlpressure chambers having a port for controlling tiuid communication operate eliciently with such leakdown tolerance control acting in conjunction with the check-valve to control the same. t

I.Another-'object provides for the novel transfer of leak- 'Lidown :highj pressure fluid to vthe low pressure chamber,

to prevent fluid loss from the tappet unit.

A further object provides for the novel operation of the tappet by direct mechanical one-way connection automatically in the event of partial or complete hydraulic failure.

It is the object of another embodiment of the invention to eliminate the inertia weight per se, and check-valve return or seating spring, and substitute the weight snubber spring for seating the check-valve.

And still another modification of the invention provides for the novel use of the inertia weight snubber spring to act directly against another movable member rather than on the check-valve mechanism which eliminates the supplemental action of said spring to hold the check-valve element seated.

Other and further objects and features of the present invention will become apparent to those skilled in the art upon a consideration of the accompanying drawings and following description wherein are disclosed three embodiments of the invention with the understanding that such changes may be made therein as fall within the scope of the appended claims without departing fromthe spirit of 'the invention.

In the drawing:

Figure 1 is a fragmentary transverse vertical section through a V-type internal-combustion engine showing the overhead valve operation mechanism incorporating selfadjusting hydraulic valve tappets constructed in accordance with the present invention;

Figure 2 is a longitudinal central section on an enlarged scale through a tappet of Figure l in the reposed r engine valve closed position with the check-valve in process of initial recovery to lightly seated condition;

Figure 3 is a view similar to Figure 2 but showing the tappet in engine valve open position with the check-valve firmly seated;

Figure 4 is a fragmentary view of Figure 3 on an enlarged scale of the inertia-controlled check-valve mechanism and associated leakdown control;

Figure 5 is a fragmentary view similar to Figure 2 but showing a modified construction wherein the checkvalve return or seating spring and inertia weight are eliminated; and

Figure 6 illustrates another modification of the invention wherein the inertia weight snubber spring acts directly against a fixed abutment.

Referring now to the drawings, and particularly to Figure l, the invention is shown incorporated in a conventional internal-combustion engine generally indicated at 10 having a plurality of poppet valves, one of which is shown at 11 cooperating with its seat 12 in closed position. A valve drive train generally indicated at VD is provided for each valve of the engine, and is conventional in all respects except for the valve tappet mechanism T of the present invention, which is embodied therein. The valve drive train or gear VD extends between the valve 11 and camshaft 15 driven by the engine. The valve 11 may be of any known construction and that selected for illustration includes a stern portion 16 guided in a press-fitted collar part 17, and having preloaded spring means 18 associated therewith normally tending to close the valve. A rocker arm 19 pivotally mounted on a suitable rock shaft 20 is adapted to bear at one end 21 thereof against the free or upper end of stem 16 when moved in a counterclockwise direction, as viewed in the figure, to open valve 11 against the force of-spring means 18. rl'he other or lower end 22 of the rocker arm 19 has a hemispherical recess (not shown) in its under surface to accommodate the upper ball end of a push rod 24, the lower end of which lextends into the open end of the valve tappet T, which will be described later.

The valve tappet T comprising the present invention, v

which is generally cylindrical in contour, is illustrated as 10 so that the inner end of the tappet bears on the surface of a cam 26 allotted thereto.

Referring now to Figures 2, 3 and 4 for a more complete understanding of the construction and functioning of the valve tappet T, it will be seen that each of these comprises as a first principal element, an outer body member 27 movably fitted into a bore 25 of the engine block, and having a longitudinal bore 28 closed at its bottom end 29 adapted to engage the surface of the cam 26 as seen in this figure. The second principal element of the tappet comprises an inner or plunger member 30 of cup-like form having a longitudinal bore 31 therein, the outer cylindrical surface thereof sliding with a substantially oiltight fit in the bore 28. The body member bore 28 is formed from substantially its medial point with a reduced diameter portion 32 terminating at its closed end. An annular shoulder 33 is formed at the juncture of the portion 32 with the upper normal diameter of the bore 28 for a purpose to be later described. The plunger 30 is closed at its inner or bottom end 34 except for a pair of axial ports 35 and an annular recess 36 provided in a central depending embossment 37. A high pressure liquid chamber H is seen to be confined between the walls of the smaller cylindrical bore 32 in the lower portion of the tappet body 27 and the inner end 34 of the plunger, which chamber when appropriately filled with oil and closed by a valve member over the ports 35 functions as a solid element to cause lift of the valve drive train by the engine cam 26 acting on the engaging end of the outer member 27. A dished element 40 is carried by the upper or open end 41 of the plunger 30 and provides a seat for the lower ball end 42 of push rod 24. For convenience in construction the seat surface engaging the ball end 42 has a conical taper as shown at 43. This provides for a circular line contact between the lower end of the push rod and the upper confronting surface of the taper 43 to facilitate proper working alignment of the parts.

An inverted cup-shaped piston 4S is reciprocally mounted in the bore 31 of the plunger to form with the circular end wall thereof, what may be termed a low pressure liquid chamber generally designated L. The lower open end of the piston carries an annular external channel 47 fitted with a pliant pressure lip sealing element 48. An annular internal groove 50 is provided in the surface of the bore 31 adjacent the open end of the plunger for reception of a split retainer ring 51. A normally preloaded compression spring 52 is operatively disposed between the piston 45 and retainer ring 51 to bias the piston toward closing chamber L.

The dished seat element 40 is spaced from the abutment ring 51 best shown in Figures 2 and 3, and preferably incorporates two angular passagcways 53 to relieve any tendency of compression on either side thereof, thus obviating fortuitous separation of this element from the plunger 30 during the tappet cycle.

A check-valve assembly CV preferably comprising a fiat circular movable disc 55 cooperating with seat 56 formed on the end of the embossment 37, serves to close ports 35 in the ybottom wall of the plunger 30. The disc is centrally apertured at 57 through which a reduced diameter portion 58 of a valve stem 59 is press-fitted to securely attach the disc to the stem for movement together at all times. The upper exposed end of the reduced portion 58 extends through a central bore 61 in the bottom wall of the plunger 30 to slidably guide the disc into proper seating relationship with its seat 56 and a lower normal diameter portion 62 of the stem forms a shoulder at 64 with the upper portion 58 with which the underside of the valve disc engages to axially stabilize the disc in that direction on the stem while the upper side of the disc is engaged by a split retainer ring 65 engaging a suitable groove 66 in Vthe outer surface of the exposed stem portion 58 whereby the disc is axially sccured tothe stem should thermal conditions tend to rclaX the press-fit thereof. An annular ange 68 forms the egsaga lower terminus of theV stem 59. A normally preloaded helically formed compression spring 70 is operatively disposed between a split retainer ring 71 received in a groove 72 formed adjacent the upper end of the stem portion 58, and the inner surface of the bottom wall`34 of the plunger being freely accommodated by the cavity of the piston 45. The normal pretensioncd status of the spring 70 is sufficient to hold the valve disc 55 lightly seated on its seat 56 as shown in Figure 2 and also to counterbalance the static weight of novel inertia mechanism generally designated 1, operably associated with the valve 55 and to be described in greater detail, when the fluid pressure forces on opposite sides of the valve disc are substantially equal; but the valve disc is readily movedV downwardly against said spring action upon the pressure forces of the liquid in chambers H and L substantially counterbalancing, however, even though the pressure on the liquid in chamber H exceeds that existing in chamber L when the tappet body is in its lowermost position exemplified in Figure 2, action of the inertia mechanism I in its downward throw is effective to move the valve disc off its seat and thus accommodate tappet adjustments according to thermal changes or wear in the valve drive gear VD. Due to the counterbalancing action of the spring 70 a slow recovery rate is provided in reseating the valve disc 55 enabling sufficient time lapse for necessary tappet adjustments to shorten or 'lengthen the valve drive train between engine valve opening cycles.

This dwell provided between opening cycles of thel engine valves is an important operationalfeature of the present tappet since tappet adjustments are accommodated over the widest possible range of camshaft movement. To this end, the camshaft 15 is Provided with a plurality of the previously mentioned cams 26, one for each tappet, and having a base circle 76, merging with an opening ramp 77 and a closing ramp 73 to form the cam lobe 79 at which maximum lift is provided. Accordingly, due to the slow recovery rate of spring 7i) in reseating the valve disc after being opened by inertia action thereagainst as the tappet body 27 engages the base lcircle 76, the valve disc remains open substantially for the full duration of tappet body engagement with the base circle to insure that proper adjusting operations in the valve drive gear VD have been effected prior to the next valve opening cycle.

The plunger Sii is constantly biased outwardly tending to enlarge chamber H, by a normally preloaded helical spring Si, the upper end of which bears against an outturned annular flange 82 of a cup-shaped member or cage S3, said flange being seated against the inner end 34 of the plunger 30, and the other end bearing against the end wall of the smaller borre of the tappet body 27. The spring 8i encircles the cage 83 and thus tends to centralize this spring as well as hold the cage against the inner endof the plunger for movement therewith. The cage is provided with a lower end wall 84 having a central aperture S5, and at the upper open end adjacent the outturned flange, a series of ports 86 are provided through the cylindrical wall to enable free ow of liquid within the chamber H between the interior and exterior of the cage.

pression spring 8SV encircles the lower stem portion 62 with its upper end normally in preioaded engagement with the underside of the valve disc 55, and the lower end bearing against the end face of a circular recess 89 formed in the upper side of an inertia weight or hammer 9?, said weight also having a central bore 91 for slidable recep- Y tion of the stern portion 62, and the lower side thereof is provided with a `circular recess 92 for reception of the annular ange 68 whereby, in the lowermost positions of the weight-9b and connected valve disc 55, the lower'end faces of Aboth the ilange 68 and weight engage the end wall\ of the cage `83' to thereby limit the downward movement of the weight and valve disc with respect tothe plunger The cage 33 and valve disc assembly CV are coaxially disposed, and a preferably conically formed comj 30. It is contemplated that a thin washer of non-metallic substance may be inserted between the wall and weight for quiet impact of the latter therewith.

A further important operational characteristic of the inertia hammer 90 resides in the force transmitted thereby through spring 88 during its upward throw induced by the lift portion of the tappet cycle, said force being effective against the underside of the valve disc 55 to supplement the action of the spring to seat and hold iirm- Y ly seated said disc during the valve opening cycle of the tappet T. Thus the inertia weight 90 cooperates with the spring 70 to close and so maintain said valve disc during the upwardV throw of the weight 90, while the downward throw of the weight following closure of the engine valve is effective to overcome spring 7i) and existent liquid pressure differentials within chamber H to open said valve disc so that the tappet can adjust the length of the valve drive linkage` VD. It thus follows that high pressures developed within chamber H at the instant of opening solid element to open the engine valves as is understood. As pointed out'above, the inertia weight 90 is loosely fitted on the stem portion 62 for sliding movement. Preferably, the circular edges on the weight are rounded to facilitate its high speed movement through the rnass of oil surrounding it. Obviously, the weight may move rela-v tively with respect to the stem 59 from its own inertia and the rapid movement of the valve tappet, causing addi,

tional compression of the spring S8 as the sleeve-type weight 9i? moves upwardly relatively thereto. When the forces are in the opposite direction, the weight 90 is` moved downwardly toward the annular abutment 68` forming the lower terminus of the stern 59 with increased speed over that resulting from inertia effect and stem movement, the additional energy being supplied by the expanding action of the buffer spring 83 to its preloaded status. When the weight strikes the abutment 68, it drives the check-valve assembly CV downwardly away from its seat 56, releasing the modulated pressure in the chamber H beneath it for purposes to be later described. This inertia weight operation is repeated with each engine valve opening cycle.

Reference is now made to the leakdown fluid control means incorporated between the longitudinal bore 28 of tappet body Z7 and the outer surface of the plunger 30. This means comprise an annular channel 94 in the outer surface of the plunger adjacent its inner end, an oil control piston ring 95 with overlapped ends fitted into said channel, a radial port 96 connecting the channel with the low pressure chamber L formed within the lower end of the plunger, an annular groove 97 in the outer surface of the piston ring, and a series of minute radial ports 98 for interconnecting the piston ring groove 97 with the channel 94, whereby liquid under high pressure escaping from the high pressure chamber H is conveyed between the controlling tolerance fit between the plunger and tappet body bore, and collected in the groove 97 of the piston ring at reduced pressure for transmission via ports 93, channel 94, radial port 96 to the low pressure chamber L. it is thus seen that as the tappet rises on the opening ramp or flank 77 of the cam 26, and the full load of the valve train is applied on the tappet, a predetermined and closely held clearance between the plunger 30 and tappet leak-down which will be discussed hereinafter in greater detail.

To prevent separation of the tappet body and plunger I when the tappet is not incorporated in an engine, a suitable split ring 101 fits into an appropriate internal groove 102 adjacent the open end of the tappet bodyy bore in `overlying relationship with respect to the outer end of the plunger, and thus limits outward movement of the plunger assembly 30. The tappet when installed in an engine (see Figure 2) establishes the plunger assembly slightly spaced inwardly from the ring 101 to condition the tappet mechanism T to perform its two-way cornpensating functions as is understood.

Operation Assuming the engine valve 11 in closed position, and the various elements of the tappet mechanism T in their relative positions illustrated in Figures 1 and 2. Here the helical spring 81 between the tappet body 27 and plunger 30 expands the tappet length between the push rod 24 and base circle 76 of the cam 26 on the camshaft so that the engaging end of the tappet biases thereon with substantially the force exerted by spring 81. Both chambers H and L of the assembly are lled with oil under pressure according to the force exerted by the piston spring 52. The weight of the check-valve seating spring 70 is such as to substantially counterbalance the static weight of the inertia hammer 90 and check-valve assembly CV into lightly seating relationship with the valve seat 56 encircling the ports 35 as shown in dashed lines.

As the engine camshaft 15 rotates in a clockwise direction as viewed in the figures, the opening ramp 77 thereon which merges with the base circle 76, operatively engages the confronting face of the end 29 of the tappet body 27 and begins to lift the latter either with a quick lift, if the cam is designed for the conventional type of hydraulic tappet, or with a slower more gentle lift if the cam is especially designed for tappets of the type of the present invention. Under these circumstances the movement of the tappet T being resisted by the engine valve spring means 18 through the push rod 24, tends to exert force on the mass of oil in chamber H causing high pressure conditions to be instantly effective due to simultaneous pressure impact on the underneath side of the check-valve 55 which is already lightly seated, and the upward throw of the inertia hammer 90 to tightly seal the ports 35, thereby imprisoning the liquid in chamber H under high pressure in a sufficiently solid acting mass to cause the parts of the valve tappet T to move in unison and lift the engine valve as if a solid tappet were in place. The engine valve train clearance having been substantially Zero at the position indicated in Figure 2 because 0f the action of the expanding spring 81 between the principal tappet body parts, the action in operating the valve drive train VD is that of a mechanical lifter with substantially zero-lash present.

When the cam valve. opening ramp 77 first strikes the under face of the tappet, all parts associated therewith are given a rapid upward thrust including the inertia weight 90 solidly seated on the annular abutment 68 of the valve stem 59. Being unrestrained in its movement except by the light buffer spring 88, the inertia weight moves more rapidly than the other parts of the tappet under the initial impetus and additionally compresses the spring 88 so that the weight moves up to the position illustrated in Figure 3 wherein its lower face is seen to be spaced well away from the valve abutment 68. This condition holds at least until the cam 26 reaches its position of maximum lift as portrayed in Figure 3 and all the time the weight 90 is compressing the spring 88 the latter reacts on the stem 59 to assist the helical spring 70 to hold the valve disc 55 tightly against its seat 56 under any tendency, such as might come from vibration or the like, to unseat it, thus insuring operation for this portion of the tappet cycle with substantially zero backlash and absolutely quiet operation of the valve train. Y

As the cam 26 progresses from the maximum lift point 79 to the release or valve closing ramp 78, the tappet is lowered and with it the engine valve 11 is closed by action of the spring means 18. Under these circumstances, the downward movement of the tappet leaves the inertia weight 90 lifted in the Figure 3 position continually imparting lift to the valve stem 59 and disc 55 whereby to maintain the latter tightly on its seat until the valve tappet T rides off of the ramp at the beginning of the base circle 76. Here conditions reverse themselves, the downward movement of the tappet T ceases, the inertia of the weight 90 no longer is suflicient to overcome the expanding action of its spring 88 and the weight, both under the influence of gravity and the pressure of the spring 88, descends rapidly, striking the upper face of the stem annular shoulder 68 and thus drives the disc 55 from its seat as shown (full lines) in Figure 2, despite the still considerable uid pressure difference which may be behind it thereby re-establishing fluid communication via ports between chambers H and L whereby an appropriate movement of oil in the right direction takes place. The spring 70 and weight means I are so weighted that at periods of rest the former predominates to lightly close the valve (dashed lines) but can be readily modulated by augmentation of the effect of spring 88 responsive to the action of the inertia weight 90.

During closure of the check-valve 55 in the manner above described, a slight amount of oil will escape from chamber H to chamber L through the ports 35 controlled by said check-valve. This function performs the essential leakdown operation of the plunger assembly 30 relatively to the tappet body 27 and consequently raises the pressure slightly in the low pressure chamber L due to additional compression of the piston spring 52. This controlled amount of oil escaping from below the plunger via ports 35 into the low pressure chamber L completes the establishing of a proper operating clearance in the valve drive linkage as the nose of the engine-driven cam approaches engagement with the tappet body during the lift portion of the tappet cycle. Therefore, as the tappet reaches the closing ramp 78 of the cam 26, the plunger 30 is lower in relation to the tappet body 27 than in Figure 2 position. As the tappet continues to ride down the closing ramp, the check-valve 55 opens, if the valve drive linkage VD has remained the same or contracted. The spring 81 between the plunger 30 and tappet body 27 compensates by taking up the clearance aforesaid and the cycle is repeated. However, if the valve drive train VD has expanded more than the relative amount of clearance or leakdown movement between the plunger and tappet body, then unseating of the check-valve 55 is not requisite since subsequent cycles will in due time take advantage of an open condition of the check-valve 55 after the expansion aforesaid has been dissipated. Therefore, when the engine structure and valve drive gear expand and contract with changes in engine operating temperatures and other differentials, the tappet T automatically adjusts its own length to compensate for such changes and wear. When temperature changes require shortening of the tappet length, the engine valve spring means 18 forces the plunger 30 down because of the leakdown characteristics, thus constantly correcting for this condition. When lengthening of the tappet is required, the tappet spring 81 raises the plunger, causing oil to ow from chamber L into the chamber H via the ports 35 controlled by the check-valve 55.

Operation of the check-valve 55 to closed position is effected by the compression spring subsequently augmented by the forces exerted by the high pressure condition within chamber H and the upward throw of the inertia hammer 90,-the latter being connected to the check-valve by the conically formed preloaded compression spring 88. This closing operation is brought about during the lift portion of the tappet cycle to insure that the ports 35 are tightly sealed to completely isolate 9 chamber H from chamber L. Upon the tappet coming into Contact with the base circle 76 of the engine cam 26, the inertia hammer 90 imparts a downward impact into contact with the annular flange 63 on the valve stem 59 to positively open the check-valve 55 and thus insure compensating movements between the plunger and tappet body prior to another valve opening cycle. The force or thrust exerted by the inertia hammer 90 in motion downwardly is of such magnitude as to overcome the biasing effect of the return spring 70 and open the check-valve, but the movement of the check-valve toward its seat 56 encircling the ports 35 is slowed due to substantially counterbalancing between the force of the check-valve seating spring '70 and the static weight of the inertia hammer 90 and check-valve assembly CV.

If there has been over compensation to reduce the clearance to less than zero (excess pressure on the base circle 76), then a certain'amount of the oil may transfer back into the chamber L, or if as the result of temperature` changes or wear in the valve drive train VD, there has beenan accumulated blacklash this is immediately taken up under the action of spring 81 forcing the tappet to elongate and again reducing the clearance to substantially zero. The slight tendency of the valve disc 55 to open resulting from its own momentum is very materially augmented by the action of the hammer blow of the inertia weight 90 moving under the impetus of its spring S8 and thus complete opening of the valve 55 is assured under all circumstances so that full compensation may be made for proper clearance adjustment.

The valve disc 55 is held open under the conditions shown in Figure 2, that is, the closing thereof to lightly seated relationship withits seat (dashed lines) is progressive during a substantial degree of arc during which the tappet body 27 engages the base circle 76 of the cam 26, but the momentum exerted by the hammer weight 90 is lost prior to approaching the opening ramp '77 so that the valve disc has lightly closed under the influence of its spring 70 in readiness for the hydraulic impact when the tappet T is again lifted on the ramp 77 to open the selected engine valve 11.

If desired, the strength of the check-valve return springV 70 may be increased to effect quicker and more effective seating thereof thus reducing or eliminating entirely the leakdown function Via said valve as previously described. In this latter instance, the leakdown would be provided by suitable clearance between the plunger and tappet body with the oil escaping from chamber H returned to low pressure chamber L via the annular channel 94 in the outer cylindrical surface of the plunger 30 and the metering port 96 interconnecting the channel and low pressure chammber L.

When the tappet T is removed from the engine for service, etc., the plunger 3i) is biased by spring 81 against the split retainer ring 101 and the low pressure piston 45 is biased into engagement with the end wall of the plunger bore 31 by spring 52, which positions of the parts correspond to the factory assembled status with both chambers H and L filled with oil. When the tappet T is installed with'the engine valve 11 closed, the push rod 24- forces ythe plunger 30 downwardly relatively to the tappet body 27 as depicted in Figure 2. This operation reduces the size of chamber H causing the surplus oil to pass via the open ports 35 into chamber L causing the piston S2 to raise to the position shown and thus establish pressure on the tiuid in both chambers in accordance with the compressed status of the piston spring 52. The tappet is now ready for its adjusting operations to compensate for backlash in the valve drive gear as is understood.

Modyed check-valve assembly and operation In the modified embodimentV depicted in Figure 5, wherein partsanalogous `to those already described are designated by like reference characters distinguished, however, by the addition of the letter a to each numeral and the exponent l to each letter, only closely associated structure of the present tappet mechanism T1 is shown, and it may be assumed that otherwise the components correspond to those of the embodiment first disclosed (Figures 1-4).

The check-valve assembly CVll comprises the valve disc 55a co-operating with valve seat 56a, a stem 110 is formed with an upper reduced diameter portion 111 slidably guided by bore 112 in the plunger end Wall 34a and press-fitted into la central aperture 57a of the disc to fix the disc on the stem for movement therewith. The annular shoulder 64a is defined at the juncture of the portion 58a with the normal diameter portion 62a depending from the valve disc, said shoulder being effective to establish the axial position of the disc on the stem, and the split retainer ring 65a engaging an appropriate groove 66a in the reduced stem portion 58a adjacent the upper side of the valve disc is provided to insure that should the pressfit of the disc on the stem become relaxed due to impact, thermal conditions, etc., that the disc cannot become displaced from its axial position against the shoulder 64a. A preloaded conical compression spring 114 is preferably employed to bias the Valve disc toward closed seated position as shown in the figure, and is operatively disposed between the underside of the valve disc and end wall 84a of the cage 83a otherwise the tappet assembly T1 is identical to the structure comprising the iirst embodiment.

ln operation, it will be noted that the inertia weight 9i) of the first embodiment is eliminated for controlling in part the action of the check-valve assembly CV1, the spring 114 being adapted to replace the spring action 70 to lightly seat the disc 55a on the seat 56a while the tappet body 27a rides the base circle 76a of the cam 26a. At the instant of the cam opening ramp 77a engaging the lower end 29a of the tappet body 27a to inaugurate an engine Valve opening cycle, the high pressure conditions induced thereby in chamber H1 co-operates with the action of the spring 114 to firmly seat the valve disc 55a on its seat 56a` and thus completely isolate chamber H1 from chamber "L1 whereby the tappet body 27a and plunger 30a move together as a solid element to operate the valve drive train VDl and open the selected valve 11a asis understood. Upon the tappet body being lowered by the closing ramp 78a onto the base circle 76a of the cam 26a to close the engine valve, the leakdown relative movement between the tappet body and plunger during the lift portion of the tappet cycle enables the compression spring 81a to relax the tappet assembly whereby the pressure in chamber H is lowered so that the spring biased check-valve disc 55a can relax its firm seating on seat 56a which places chamber L1 and H1 in communication with cach other for the adjusting operations of the tappet assembly T1 to ensue should such be required.

Accordingly, in `this modification, the inertia means I is eliminated placing check-valvel control on the conical spring 114 formerly employed to impart accelerated downward throw to the inertia weight 90.

Modified inertia mechanism and operation In the modification shown in Figure 6 parts analogous to those already described are designated by like reference characters distinguished, however,` by the addition of the letter b to each numeral and the exponent "2 to each letter. This arrangement is essentially similar to that Y of the first described embodiment (Figures l4), except and the lower end has a central annular opening 124A asoaaaa formed by extrusion of a portion ofthe end Wall, the latter serving as a guide and seat for the upper end of the spring 120 as illustrated, while the opening accommodates the valve stern 59h to freely project therethrough for actuation by the inertia member 90b, the latter being acted on by the lower end of the spring 120 seated in the recess 89b. Accordingly, the upward throw or movement of the hammer 90b is not transmitted to the valve disc 55b during the lift portion of the tappet T2 cycle, but upon completion of a valve opening cycle with the tappet T2 riding the base circle 76b of the cam 26b, the additionally compressed inertia spring 120 imparts an accelerated impact of the hammer 90b against the stem flange 68b to overcome the action of spring 70b, and differential pressure conditions acting on opposite sides of the valve disc 5517 to unseat the latter from its seat Sb and thus place chambers H2 and L2 in communication with each other to equalize the pressure therebetween thus enabling compensating adjustments as maybe required between the tappet body 27b and plunger 301; in readiness for the next valve opening cycle as is understood.

Accordingly, in this third embodiment of the present invention, the supplemental action of the upward throw of the inertia weight 90b is dispensed with to assist the check-valve seating spring 70b, while the downward throw thereof is retained to effect opening of the checkvalve 55b.

Operational summary Although the manner in which my invention achieves its objectives should be manifest from the foregoing description augmented by an inspection of the drawing, a brief restatement is deemed apropos, and will be given as follows:

What will be considered a tappet cycle, will now be described with reference to the tappet of the instant invention: Figures 2 and 3 show the tappet T in two cam positions, respectively. Figure 2 position shows the tappet on the base circle 76 of the cam 26. In this position, the spring 81 in the tappet takes up all the clearance in the valve drive gear VD. At the same time the check-valve disc 55 has recovered from the full line open position to the lightly seated position shown in dashed lines. Pressure on the liquid contained in chamber H and L is substantially equalized and the inertia hammer 90 occupies its lowermost position relatively to the valve stem portion 62 in contact with the annular abutment 68.

As the tappet T is raised by the cam 26 to Figure 3 position, the oil below the plunger 30 in the chamber H tends to escape past the check-valve disc 55. This rush of oil around the lightly seated disc 55 forces the disc to seat on the plunger embossment 37 which seals the ports 35 at the bottom of the plunger 30 and the tappet then follows the cam as a relatively solid unit. The travel of the check-valve disc 55 is closely controlled which results in a slight relative movement between the plunger 30 and the body 27 to firmly seat the disc 55.

As the tappet T rises on the flank or opening ramp 77, and the full load of the valve drive train VD is applied on the tappet, a predetermined and closely held clearance between the plunger 30 and body 27 enables a controlled amount of oil to escape from chamber H past plunger 30 via oil control ring 95 into low pressure chamber L. This condition-the relative movement of the plunger 3ft with respect to the body 27 during firm seating of the tappet disc 55-is termed leakdown previously referred to. As the tappet body 27 reaches the nose 79 of the cam 7.6 as shown in Figure 3,-the plunger 39 has leaked down a very minute distance relatively to the body 27 as compared to its position portrayed in Figure 2. Consequently, as the tappet T reaches the closing ramp 7g, the plunger 30 is lower in relation to the body 27 than in Figure 2, where the disc 55 has just seated (dashed lines). As the tappet continues to ride down the closing ramp 78, the check-valve 55 opens if the valve drive gear has remained the same or contracted,

which opening operation is assured by the impact of the downward throw of the inertia hammer 90 at the arrested point of the tappet resulting from engagement with the base circle 76. The spring 81 under the plunger 30 compensatesl by taking up clearance and the tappet cycle is ready to be repeated as is understood. However, if the valve linkage VD has expanded more than the relative amount of movement (leakdown) of the plunger 30y in the body 27, then the check-valve 55 will not unseat until the inertia hammer action becomes effective as aforesaid. Therefore, when the engine block and valve drive gear expand and contract with changes in engine temperatures and other differentials, the tappet T automatically adjusts its own length to compensate for these changes. When temperature changes require shortening of t'ne tappet length, the engine valve spring 13 forces the plunger 30 down because of the opening of the valve disc 55 by the inertia hammer 90 with each cycle of the tappet-leakdown is not relied upon as in conventional hydraulic tappets, thus constantly correcting for this condition with the excess oil in chamber H transferring the chamber L with attendant raising of piston 45. When lengthening of the tappet is required, the tappet spring 81 raises the plunger 30, causing the excess oil in chamber L to flow via open disc 55 and ports 35 into the high pressure chamber H with piston 45 correspondingly lowered. It is thus seen that the leakdown" function is utilized or made effective during the lift portion of the tappet cycle to provide an appropriate operating clearance in the valve drive gear when opening the engine valve 11, so that, when the tappet relaxes on the base circle 76 of the engine driven cam 26 the inertia influenced opening of the check-valve 55 is assured under all operating conditions irrespective of the differential pressures effective across opposite sides of the disc and the biasing action of the spring to close said disc.

Further considering the various illustrations of the different embodiments of my invention, it will be appreciated that certain inter-related components of the tappet mechanism T possess similar functional characteristics such that interchangeability is readily effected, particularly in respect to leakdown control. For example, it is important to note here that the oil control ring 95 may be dispensed with in favor of tolerance control between the plunger assembly 30 and tappet body 27 to prevent loss of fluid from the high pressure chamber H. In the latter arrangement, the lightly seated condition of the check-valve CV would be effective to provide the necessary relative leakdown prior to firm seating of the element 55 to completely isolate the two chambers H and L. From this it follows that the preloaded status of the spring 70 determines the degree of effective seating of the check-valve aforesaid prior to an opening cycle of the valve drive gear,'and that this spring is supplemented by the high pressure liquid forces within chamber H and the action of the inertia weight to firmly seat the check-valve concurrently with the relative leakdown function of the present tapept mechanism, whether such controlled escape of oil is via the tolerance fit bctween the tappet body and plunger and/or the lightly seated check-valve element 55, into the low pressure chamber L. Accordingly, any change in the quantity of oil in chamber H as a consequence of leakdown and/ or compensation for thermal changes or wear is accommodated by modulation of the piston spring 52.

Further beneficial results in the operation of an engine equipped with my present tappet mechanism may also be realized in the selective use of differently rated springs for controlling the seating of the check-valve 55 and action of the inertia weight 90. That is to say, the spring 7G as illustrated in Figure 2 is preferably designed to effect slow recovery of the check-valve mechanism including the inertial weight 90 to a lightly seated condition shown by dashed lines in this figure. This cycle of operation of the tappet is effective substantially through t 13 t the full arc of base circle rotation of'. the cam 26. The relative positions of the parts depicted in this figure correspond to engine valve closure at the instant the inertia hammer 90 has completed its downward throw to fully open the check-valve 55, with spring 70 acting to start recovery of the check-valve to lightly seated con dition (dashed lines) which condition will prevail before the tappet body-engages the opening ramp 77V of the engine cam 26. However, if spring 70 is made stronger, closure of the check-valve will occursooner and more effectively, therefore, less time will be given for tappet adjustments, and such closure under the influence of a stronger spring will further inhibit leakdown via the disc 55 and requires aV correspondinglystronger spring 38 for imparting increased `acceleration tothe hammer 90 in its downward throw. It is thus seen that by varying the relative strengths of the springs 70 and 88, operational behavior of the tappet T is modified to suit the operational characteristics of the engine.

With the functioning of thefirst embodiment (Figures l-4) of my invention, it is clear that maximum efficiency of the hydraulic valve tappet T is assured under all circumstances, and that, substantially zero-lash is achieved in the valve drive gear VD during the full cycle of engine valve operation. After engine valve closing and when the tappet valve 55 is open there is some slight relief of pressure on the heel or base circle 76 of the cam 26 so that minimum wear results'on the contacting parts. Withthe tappet valve 55 opening and closing once per cycle careful modulation and adjustment of the whole valve train is achieved that many times, so that backlash or lost-motion in the whole train is maintained as near zero as is feasible andvdesirable, all with the addition of only a few very small and inexpensive parts to what has been considered as the normal or commercial type of hydraulic valve tappet which has the tendency of becoming set thus devoided of the all important compensating function. This condition of becoming static or inoperative insofar as the capability of adjusing is brought about by use of the engine lubricant impelled into the tappet body by the pressure lubricating pump. This oil becomes contaminated, gummy, etc., tending to seize the parts of the tappet together and thus either impairing its relative adjusting efficiency or prohibiting such adjustments locking the body parts together in a set position. The present tappet also eliminates the added cost required to machine the various oil passageway'systems in the engine block to supply oil to conventional hydraulic tappets which latter also tend to become set due to erratic functioning of the usual ball or disc-type of check valve that depends solely on relaxation of the high pressure thereagainst to open so that compensating adjustment between the tappet parts may ensue. The present invention includes the novel inertia mechanism l to positively open the check-valve with the closure of the engine valve and thus insure the operativeness of the tappet to adjust.

The embodiment of the invention illustrated in Figure 5 eliminates the inertia mechanism I and spring tl and substitutes therefor a spring 114 for controlling the valve disc 55a. This spring is so rated as to substantially prevent the valve disc 55a from firmly seating during valve tappet engagement with the base circle 76a of the 'engine cam 26a, thus accommodating the lifter adjustment as required; i. e., shortening or lengthening of the valve actuating linkage.

The embodiment of Figure 6 utilizes the downward throw of the inertial weight 90b to open the valve disc 55h, thus obviously the weight has no effect in serving to close and hold shut the valve disc 55b since its upward throw is wholly independent thereof. Spring 7Gb is of such weight as toA substantially conuterbalance the static weight of the hammer 90b and connected check-valve mechanism CV2 so that the latter is operated into a lightly seated condition as shown in dashed lines prior to the f4 tappet body being engaged by the engine cam opening ramp 77h. When the weight is actuated by inertia it is cushioned in its upward movement during the engine valve opening cycle by buffer spring 12d which spring then adds to its acceleration on its downward movement to insure opening of the valve disc SSb. Note that in this arrangementV the upperend of the spring 120 is fixed whereas. in the rst embodiment the upper end of spring 8S corresponding to spring 12) engages the underside of the valve disc 5519 and moves with it.

In the three embodiments of the present invention, the spring-loaded piston @S5 always tends to open the valve disc 55 when pressure in chamber H equals or falls below that in chamber L, thus in effect co-operates with the downward throw of the inertia hammer 9) under such conditions, whereby fluid comunication is established via ports 35 between the two chambers H and L enabling relative adjustments between the tappet body members, 2.7, 3f) as required.

It will be noted that the two principal elements operate to eliminate -any backlash in the valve drive train, and both function during the time that the tappet is riding on the base circle 76 of the cam 26, as set out in the foregoing description.

The present invention also contemplates integration of the movable element of the inertia means I with the valve element stern 59 so that the hammer 90 of suitable design would move simultaneously with the stem and attached disc 55 making the spring means 83 unnecessary, to provide in effect inertial action at the point of arrested tappet motion to open the valve disc 55 in the manner already described, While the inertial upward ythrow of the check-valve assembly CV augmented by the influence of spring 70 and pressure conditions within chamber H would serve to firmly seat said assembly during the lift portion of the tappet cycle.

Further considering the operational behavior of the embodiments utilizing the spring 7tl, it is important to note that the inertial effect on the hammer 9) produced by the reciprocable movement of the tappet assembly T, particularly the lift phase causing upward throw of the hammer, requires control to prevent unseating of the valve disc 55 at the instant of lift inauguration. Movement of theV plunger assembly 30 which includes the check valve 55 and weight 90 suspended by spring 7l), is initially accelerated at a higher rate than the suspended assemblies noted when the lift phase of the tappet cycle begins. This differential in the accelerated rates between the tappet body proper and relatively movable parts aforesaid momentarily advances the plunger 3@ ahead of the static positions of these associated parts tending to unseat the check-valve disc 55. To insure against such valve unseating influencesbecoming effective, the load factor of the spring 70 is critical requiring accurate rating of this spring to restore the check-valve and hammer assemblies CV and I respectively, to seated position of the disc 55' with sufficient biasing action thereon supplemented by the high pressure condition within chamber H across the underside of the disc 55, to prevent fortuitous displacement of the disc 55 from its seat 56 at the instant the engine-driven cam 26 engages the tappet to inaugurate a selected engine valve opening and closing cycle.

The present invention is particularly adapted lto be utilized in the replacement of all valve tappet mechanisms whether mechanical or hydraulic. While it is preferred that the cam design be conventional, as shown in the drawing, it is clear that the present invention will operate satisfactorily with Vthe particular cam design presently used Vfor commercial hydraulic valve tappets where the ramp gives a rapid rise to the tappet in order to provide the hydraulic impact to insure the closing of the tappet valve substantially at the instant of initial tappet lift.

Considering the terminology used in the foregoing description and in the appended claims, the identifying eX- pressions and/ or terms employed are intended to convey meanings which include the range of reasonable equivalents in the patent sense. For example, the expressions member, body, plunger are intended to include any liquid filled casing and/or chamber having a pressure-responsive movable assembly therein, whether such assembly includes a spring-loaded piston or diaphragm, or some other member serving the same purpose. The terms top, bottom, upward, downward, and other directional words or characters are intended to have only relative connotation for convenience in describing the structure as illustrated, and are not intended to be interpreted as establishing any definite position of the tappet or requiring any particular orientation with respect to associated structure external to the present disclosure.

Although it will be apparent that the preferred embodiments of the invention herein disclosed are well calculated to fulfill the objects above stated, it will be appreciated that I do not wish such to be limited to the exact construction and /or arrangement of parts shown, since it is evident that modifications, variations, changes, and substitutions may be made therein without departing from the proper scope or fair meaning of the subjoined claims.

Having thus described my invention, I claim:

l. A hydraulic compensating tappet comprising a pair of inter-fitting relatively movable cylindrical members each havng a longitudinal cylindrical bore open at one end and closed at the other: a high presure chamber formed between said closed ends; normally preloaded compression spring means operably disposed within the high pressure chamber and acting on said closed ends for biasing said members apart and accommodating their movement toward each other; a spring-loaded piston reciprocably mounted in the bore of one of said members; a low pressure chamber formed between said piston and the closed end of said one member and effective on increase of spring load on said piston; a valve port in the closed end of said one member normally open to establish liquid communication between said chambers; liquid for normally charging both of said chambers at atmospheric pressure without increase of spring load on said piston; checkvalve means including a movable element operable relatively Ito the closed end of said one member for controlling said port; and means supplemented by liquid pressure created within said high pressure chamber responsive to tappet motion for seating the check valve element against said port during the lift portion of the tappet cycle. l

2. A hydraulic compensating tappet comprising a pair of inter-fitting relatively movable cylindrical members each having a longitudinal cylindrical bore open at one end and closed at the other: a high pressure chamber formed between said closed ends; normally preloaded compression spring means operably disposed within the high pressure chamber and acting on said closed ends for biasing said members apart and accommodating their movement toward each other; a spring-loaded piston reciprocably mounted in the bore of one of said members; a low pressure chamber formed between said piston and the closed end of said one member and effective on increase of spring load on said piston; a valve port in the closed end of said one member normally open to establish liquid communication between said chambers; liquid for normally charging both of said chambers at atmospheric pressure without increase of spring load on said piston; check-valve means including a movable element operable relatively to the closed end of said one member for controlling said port; and inertia means including a movable element operatively associated with said checkvalve means supplemented by liquid pressure created within said high pressure chamber responsive to tappet motion for seating the check-valve element against said port during the lift portion of the tappet cycle.

3. A hydraulic compensating tappet comprising a pair of inter-fitting relatively movable ,cylindrical members each having a longitudinal cylindrical bore open at one end and closed at the other: a high pressure chamber formed between said closed ends; normally preloaded compression spring'rneans operably disposed within the high pressure chamber and acting on said closed ends for biasing said members apart and accommodating their movement toward each other; a spring-loaded piston reciprocably mounted in the bore of one of said members; a low pressure chamber formed between said piston and the closed end of said one member and effective on increase of spring load on said piston; a valve port in the closed end of said one member normally open to establish liquid communication between said chambers; liquid for normally charging both of said chambers at atmospheric pressure without increase of spring load on said piston; check-valve means including a movable element operable relatively to the closed end of said one member for controlling said port; and preloaded compression spring means supplemented by liquid pressure created within said high pressure chamber responsive to tappet motion for seating said check-valve element against said port during the lift portion of the tappet cycle.

4. A hydraulic valve tappet comprising a pair of relatively movable members defining a high pressure liquid chamber therebetween, a piston reciprocably mounted in one of said members, a normally preloaded expansion spring acting on said piston, a low pressure liquid chamber formed between the piston and said one member, a valve port in said one member normally establishing liquid communication between said chambers, a check valve adapted to close said port against pressure in the first-mentioned chamber, a normally preloaded compression spring for biasing said check-valve to close said port, a normally preloaded expansion spring for biasing said pair of members apart, inertia means comprising a weight slidable longitudinally of the tappet relatively to the ported member, means guiding the weight to act on the check-valve to open the same against its biasing spring when tappet motion stops after downward movement, and liquid for normally charging both of said chambers without modulating the preloaded status of said piston spring.

5. The tappet according to claim 4 including normally preloaded spring means operatively acted on by said inertia weight for additional compression thereby during upward motion of the tappet.

6. The tappet according to claim 5 in which said lastmentioned spring means are operably positioned between an abutment immovable on said ported member and the inertia weight, the latter normally engaging a shoulder formed on said guiding means in spaced relation with respect to said check-valve.

7. The tappet according to claim 6 including another abutment immovable on said ported member for defining the limit of downward throw of the inertia weight and open position of said check-valve.

8. The tappet according to claim 7 including tolerance leakdown control between said pair of members and a liquid passageway leading therefrom to said low pressure chamber for conveying liquid escape from the high pressure chamber to the low pressure chamber resulting from such limited relative movement between said pair of members during the lift portion of the tappet cycle.

9. The tappet according to claim 7 including piston ring control between said pair of members and a liquid passageway leading therefrom to the low pressure chamber for conveying escape liquid from the high pressure chamber to the low pressure chamber during the lift portion of the tappet cycle.

l0. The tappet according to claim 7 including an element carried by each of said members in confronting spaced relationship for engagement in the event of partial or complete failure of the hydraulic control, to provide a one-way thrust mechanical connection for simultane- Iiously actuating the pair of members during the tappet cycle.

ll. A hydraulic valve tappet comprising a cup-like body portion adapted for cam actuated reciprocation in a motor block, a cup-like plunger reciprocably nested in said body portion to dene a high pressure liquid chamber therebetween, a normally preloaded expansion spring in said chamber tending to enlarge it, a push-rod cup nesting in said plunger, a piston reciprocably mounted in said plunger between said push-rod nest and the closed end thereof to form a low pressure liquid chamber therebetween, a normally preloaded expansion spring acting on said piston to decrease said low pressure chamber, a port in the closed end of said plunger normally establishing liquid communication between said chambers, a check-valve disc co-operating with said port and located within said high pressure chamber, liquid for normally charging both of said chambers without modulating the preloaded status of the piston spring, a normally preloaded spring for biasing said disc to close the port, an inertia weight effective to bear on said disc when the tappet is at rest, and means in said high pressure chamber for guiding said weight for reciprocation on the axis of movement of the tappet.

12. The tappet according to claim 11 in which the weight is a sleeve and the guiding means comprise a rod entering a hole parallel with said port.

13. The tappet according to claim 12 in which the weight is formed with a central opening for reception of the rod and the upper and lower ends with circular recessed portions.

14. The tappet according to claim 13 in which a normally preloaded buffer spring is mounted on said rod, one end of said spring being seated in the upper recess and opposite end engaging the closed end of said plunger whereby it is additionally compressed when inertia causes a relative upward movement of the weight against it.

15. The tappet according to claim 14 in which said rod is rigidly attached to the disc and slides in said hole in the closed end of the plunger.

16. The tappet according to claim 15 in which the lower end of the rod carries a circular shoulder received by the lower recess in the weight for engagement thereby.

17. The tappet according to claim 12 in which the upper end of the rod is rigidly secured in the hole and the free end thereof is spaced from the disc.

18. The tappet according to claim 17 in which the spring biasing said disc is mounted on said rod and interpositioned in engaging relationship with two spaced abutments immovable on said plunger.

19. In a hydraulic compensating valve tappet for internal-combustion engines including a cam-actuated tappet body having a longitudinal cylindrical bore closed at one end and open at the other; a hollow plunger reciprocable in said bore and providing a high pressure liquid chamber with said tappet body; normally preloaded spring means for axially elongating said tappet body and plunger assembly relatively to each other; a piston reciprocably mounted in the hollow of said plunger; a low pressure liquidv chamber formed between the piston and inner end of said plunger; normally preloaded spring means for normally biasing said piston to close the low pressure chamber; a valve port in the inner end of said plunger forming a valve seat for interconnecting both of said liquid chamber; an inwardly opening valve element engageable with said valve seat to close the valve port; normally preloaded spring means for biasing said valve element into engagement with said valve seat to close the valve port; liquid for normally charging both of said liquid chambers without aiecting the preloaded status of the piston spring means; and inertia means operably acting on said valve element responsive to tappet movement for supplementing the biasing action of said last-named spring means and pressure created within the lirst-mentioned chamber, to control said valve port during the tappet cycle.

20. The hydraulic compensating tappet according to claim 19 in which said inertia means include a movable element responsive to tappet motion, and normally preloaded spring means operatively energized thereby during the lift portion of the tappet cycle for subsequently accelerating the downward motion of said movable element into impact with said valve element to open the same substantially at the arrested point of tappet motion.

21. The hydraulic compensating tappet according to claim 20 in which the said plunger carries an abutment for limiting the accelerating eectiveness of the inertia means influenced by said last-named spring means.

22. The hydraulic compensating tappet according to claim 2l in which the third-named spring means are effective to substantially counterbalance the static weight of the inertia means and valve element at substantially closed position of said valve element.

23. The hydraulic compensating tappet according to claim 21 in which the third-named spring means are effective to substantially counterbalance the static Weight of the inertia means and preloaded status of the fourthnamed spring means at substantially closed position of said valve element.

24. The hydraulic compensating tappet according to claim 23 in which the third-named spring means are disposed between a portion of the abutment means carried by the plunger and the inertia movable element whereby the upward movement of the latter is ineffective to intluence closing of the valve element.

25. The hydraulic compensating tappet according to claim 2l including tolerance leakdown control between said body and plunger and a liquid passageway leading therefrom to said low pressure chamber for conveying liquid escape from the high pressure chamber to the low pressure chamber resulting from such limited controlled relative movement between the body and plunger during the lift portion of the tappet cycle.

26. The hydraulic compensating tappet according to claim 21 including piston ring liquid control operably effective between said body and plunger and a liquid passageway leading therefrom to said low pressure chamber for conveying liquid escape from the high pressure chamber to the low pressure chamber during the lift portion of the tappet cycle.

27. The hydraulic compensating tappet according to claim 2l including a pair of elements carried by the body and plunger in confronting spaced relationship for engagement in the event of partial or complete failure of the hydraulic control, to provide a mechanical one-way thrust connection for simultaneously actuating the body and plunger during the tappet cycle.

References Cited in the file of this patent UNITED STATES PATENTS 

